Cone diaphragm for loud-speakers



April 17, 1951 c. E. sTEvENs GONE DIAPHRAGM FOR LOUD-SPEAKERS Filed June17, 1947 .n.ulnlhnhnhnnn 1. l, lllbnllf;

INVENTOR. Stevens Patented pr. 17, 1951 CONE DIAPHRAGM FOR LOUD-SPEAKERSClifford E. Stevens, Glen Ridge, N. J., assignor to Stevens ProductsInc., East Orange, N. J., a corporation of New Jersey Application June17, 1947, Serial No. 755,046

3 Claims.

This invention relates to cone diaphragms for radio loud-speaker unitsand to a method of producing the same. The object of the invention is toprovide a one-piece cone diaphragm having a plurality of contiguoussectioned parts comprised of the same material with each said part beingformed specially to respond to vibrations in one of the frequency rangescommonlyreferred to by those skilled in the art as the high, W andmedium ranges Within the broad range of audio frequency to be covered bysaid diaphragm, namely, 60 to 10,000 cycles.

Another object is to provide a one-piece cone diaphragm Vfor radioloud-speakers having a plurality of contiguous sections each formedspecially to obtain a high responsivity and high fidelity of tonereproduction in said part for a selected range of frequencies covering arange from very low to very high.

Still another object is to provide an improved cone speaker diaphragmfor radio loud-speaker units characterized by a frequency response rangeas high as 10,000 cycles to as low as 60 cycles and by high sensitivity.

Other objects Willbe apparent as the invention is more fully hereinafterdisclosed.

In accordance with these objects I have discovered that the frequencyresponse range of the one-piece, cast, cone diaphragm product formed inaccordance with the method and apparatus disclosed in Stevens Patent No.2,411,066 dated November 12, 1946, which patent is assigned to the sameassignee as the present invention, is

materially increased and improved by corrugating an annular area in thelower half of the cast cone body but spaced above the relatively thincorrugated peripheral edgeportion of said body, to increase thecompliance and responsivity of the body to vibrations in the medium orintermediate frequency range and by compacting or compressing the upperhalf of said cast cone body to a thickness materially less than the castthickness of the lower half of the said body to increase the sensitivityand responsivity of the body to vibrations lying in the high range offrequencies, the uncorrugated portion of the lower half of the cast conebody providing responsivity to frequencies in the low range offrequencies and the corrugated relatively thin sectioned edge portion ofthe cast cone body providing the necessary iiexibility and vibrationdampening properties to the finished cone speaker.

The present invention is adapted to Wide medification Without essentialdeparture therefrom, as one skilled in the art Will recognize from the2, following specincembodiment disclosure thereof. In the manufacture ofone-piece, cast,` cone diaphragm bodies in accordance With the inventionof the above identified Stevens patent, a cone-shaped body having aperipheral and annular edge section of materially less thickness thanthat of the cone body is obtained, which edge section is corrugated intoa plurality of reverse bends in the area adjacent the thicker bodysection leaving an outwardly extending fin edge section having a Widthadapting the same to be secured in a vibration-free joint to an annularsupport member of the radio loud-speaker'unit surrounding the vibratingvoice coil of the loudspeaker to Which'the cone apex is fixedly secured.

The corrugated thin section of the cone diaphragm dampens the coneVibrations and prevents the same from passing to the annular supportmember.

The particular type and kind of paper pulp employed in the forming, bythe casting method of said prior patent, of the cast cone diaphragm,controls' or regulates the over-all frequency range responsivity of thecone diaphragm. Many different types and kinds of paper pulp mixturesmay be employed. With any given paper pulp mixture, the responsivity ofthe vcast cone diaphragm varies with variation in cone thickness and thesensitivity range varies with variation in the density of the cone atany giventhickness. It is, therefore, believed apparent that Where it isdesired, as in the case of cone diaphragms for radio loud-speaker unitsto provide a cone diaphragm uniformly responsive and sensitive tovibrations Within the Wide'range of 60 to 10,000 cycles, it is extremelydiflicult to attain that result in a cast body of4 uniform thickness anddensity from apex to peripheral edge. The provision of a peripheral edgesection of relatively thin section as compared to the body part,ccrrugated to impart flexibility to the section and to leave anextending annular nn of thin section to be fixedly secured to theannular cone support member, markedly improves the responsivity of thebody to vibrations in the low frequency range and effectively dampensthe cone vibrations from passing to the support member.

The frequency range of responsivity of such a cast cone body (withcorrugated thinner annular edge section) depends upon the composition,thickness and density of the body. Of the many different types and kindsof paper pulp available for use in the cast-forming of the cone body bythe method of said prior patent a mixture known in the art as a softbeaten, long fiber, hydrated 3 Krafft pulp has been found to provide thebest and widest responsivity range. With this type of pulp a cone bodyhaving a thickness (as cast) of .016 to .017 inch has an effectiveresponsivity range of from 60 to 6000 cycles.

I have discovered that by compressing the apex area of the cone body foran extended distance downwardly from the apex the sensitivity of thecone to vibrations of all frequencies in the range 60 to 6000 cycles ismarkedly increased and that the responsivity range of the cone may beincreased to as high as 10,000 cycles.

I have further found that by corrugating a part of the uncompressed areaof the cone below the compressed, higher density apex area, theresponsivity and sensitivity of the cone to vibrations in the middle orintermediate range of frequencies is augmented or improved to such anextent that the overall responsivity and sensitivity of the conediaphragm to all frequencies within the range 60-6000 cycles is mademore uniform and acceptable for use with radio loudspeaker units of thevibrating voice coil type.

As one specic embodiment of the present invention, but not as alimitation thereof, I will describe the same as it has been adapted tothe treating of one-piece cone diaphragms, formed by the method of theStevens patent, above identified, comprised of the specific andpreferred paper pulp composition above identified.

Before further disclosure of this specific embodiment, reference shouldbe made to the accompanying drawings wherein:

Fig. 1 shows, partly in section, a one-piece cone diaphragm of the typeand kind formed by the casting method and apparatus of the Stevenspatent, above identified;

Fig. 2 shows, partly in section, the one-piece cone diaphragm of Fig. 1as shaped and molded in the first step of the present invention; and

Fig. 3 shows, partly in section, the one-piece cone diaphragm of Fig. 2after treatment in accordance with the second step of the presentinvention.

Referring to Fig. 1, the one-piece cast diaphragm illustrated is of thetype known generally in the art as a inch cone, which is the diameteracross the base of the cone. The cone height is normally about 21/4inches from base to flattened, or cut-off, apex. The cut-ofi apex isnormally provided to provide for the use of a cone-shaped plug memberadapted at its apex to be secured to the end of a vibrating voice coiland about its periphery to the cut-olf edge of the cone apex.

In the as-cast condition shown in Fig. 1, the width of the thinnersectioned peripheral edge part A of the cone approximates 2% inch andthe width of the body part or cone area B from the inner edge of part Ato the cut-off apex thereof approximates 4%. inches.

After removal from the casting form,.the cone body is placed in aforming die wherein it Vis shaped or'molded, without materialcompaction, in a manner and Yby means old and well known in the art, tothe shape and congurationindicated and shown in Fig. 2. In this stepofthe present invention, the thinner sectioned part A is corrugated over apart, approximating 1/2 of its width, in the area c next adjacent lthethicker cone body part, and provided with a plurality of semi-circularreverse bends imparting to the part A in this area c a high degree offlexibility and leaving a peripheral fin extension f thereon extendingin the plane of the cone base of thin sec- 4 tion for vibration-freeattachment to an annular support member commonly provided for mountingthe cone diaphragm in a radio loud-speaker device.

At the same time the lower half of the body part B also is corrugatedover an extended width downwardly from the upper uncorrugated apex areain a plurality of reverse bends substantially semi-circular in contour,the total number of Such corrugations being widely variable withoutessential departure from the present invention but in no case coveringthe entire lower half of the cone body B.

The corrugations e in the lower half of cone body B improves markedlythe compliance of and the responsivity of the diaphragm to vibrationfrequencies in the intermediate range of frequencies. The uncorrugatedarea h of the lower half of body part B appears necessary to retaintherein full responsivity in the lower range of frequencies. In general,I have found that with the specific composition and thickness of castcone body involved, the width of uncorrugated part h should approximate3A inch and the width of corrugated part e should approximate 11/2inches for best results as to responsivity in the lower and middleranges of frequencies.

The uncorrugated' upper area g has a fairly good responsivity tovibrations in the range of frequencies above the middle range and up to6000 cycles but its sensitivity is relatively low. Various expediencieshave heretofore been employed to increase the sensitivity, such as, forexample, the use of various stiffening agents, such as shellac andresins, applied to the surface of the cone to overcome the normalreluctance of the cast ber structure to pick up the voice coilvibrations promptly.

I have found that by compressing or compacting this area g betweenco-operating male and female dies, in a manner which is, per se, old andwell known in the art, to thereby increase the density of the part grelative to that of parts e and h, the sensitivity of the cone diaphragmis increased markedly and materially and at the same time theresponsivity range is increased from a high of 6000 cycles to as high as10,000 cycles which is about the maximum frequency for audibilityrequired in such cone diaphragms.

The extent to which the density of part g is increased by suchcompaction may be varied widely Without essential departure from theinvention. I have found that generally with the specic fiber compositionemployed in the cast cone body above noted, a reduction in thickness inthe upper half of the cone body from 25% to 35% produces excellentresults on both sensitivity and responsivity. That is to say, that withan original thickness of .016 to .017 inch in the part y, compaction ofthe part to a thickness of from .010 to .012 inch provides excellentsensitivity and raises the responsivity range of the cone body fromabout 6000 up to 10,000 cycles.

vIt is believed that the smoothing of the surface of the area includingpart g as a result of the pressure applied thereto during compressing,or compacting, this area to lesser thickness and higher density resultsin the increase in the responsivity range and that' the ystiffening ofthe part g as a resultV of such compaction to lesser thickness resultsin the increase in the sensitivity of the cone diaphragm. n

The nal cone diaphragm product is shown in Fig. 3. The severalcontiguous parts f, c, h, e

and y thereof, each comprised of the same macrial and forming aone-piece cone body, are appropriately identified with the relativethicknesses and widths of each closely approximated as to scale ashereinabove disclosed in the specific embodiment given.

It is believed apparent from the above disclosure that with differentpaper pulp compositions used in cast-forming the cone body, the initialthickness and density of body parts A and B thereof may be varied widelywithout essential departure from the invention as may also the relativewidths of contiguous parts f, c, h, e, and g thereof, and the extent ofcompaction applied to part g. It is believed well within the expectedskill of one skilled in the art to so correlate the same to obtain theimproved result of the present invention from the disclosure hereinabovegiven, and all such modications, variations and departures from thepresent invention are contemplated as may fall within the scope of thefollowing claims.

What I claim is:

l. A cone-shaped diaphragm for a radio loudspeaker unit of the vibratingvoice coil type,

said diaphragm consisting of a one-piece coneshaped body consisting ofsubstantially the same fibrous material throughout, said body having aplurality of contiguous annular areas with each said area formedspecially to have a high responsivity to a desired range of vibrationfreduencies within the broad range ofireduencies from about 60 to about10,000 cycles, and said areas consisting of an apex area extending overabout the upper half of the cone body, an intermediate annular areaextending over the upper part oi the lower half of said cone body, anannular area covering the lower part or" the lower half of said conebody, and a peripheral edge area, the said apex area having a lesserthickness and a higher density than the thickness and density of thelower half of the said cone body, the intermediate annular area of thelower half of the said cone body being corrugated into a plurality ofreverse bends butI otherwise being of the same density and thickness asthe uncorrugated annular area in the lower half of said cone body, andsaid peripheral edge area being of the same density but of lesserthickness than the lower half or" said cone body being corrugated in theannular area next adjacent the cone body having a peripheral finextension thereon.

2. A radio loud-speaker cone diaphragm characterized by having a highvresponsivity to low, intermediate and high frequency vibrations overthe range of frequencies from about 60 to 10,000

tally the same fibrous material throughout, the upper half of the saidbody having a lesser thickness and a higher density than the lower halfof the said body and the lower half of the said body being corrugatedinto a plurality of reverse bends over an extended area materially lessthan the entire area leaving the area next adjacent the cone edgeuncorrugated, said cone edge being provided with a n extension of thesame density as the lower half of the cone but of lesser thicknesscorrugated in a plurality of reverse bends in the area next adjacent thecone edge, said fin extension lying in the plane of the base of the conebody.

3. In a radio loud-speaker cone diaphragm, the improvement whichcomprises a one-piece cone-shaped body provided with four contiguousannular areas, each shaped specially to impart specific properties tothe cone body, said areas comprising an apex area extending over aboutthe upper half of the cone body, an uncorrugated edge area extendingover a part of the lower half of the cone body upwardly from the coneedge, an intermediate corrugated annular area lying between the edgearea and the apex area, and a peripheral 1in extension corrugated in thearea next adjacent the said edge area, said n extension area lying inthe plane of the base of the cone body, the density of said finextension approximating that of the lower half of the said cone body butthe thickness thereof being materially less than the thickness of thelower half of the said cone body and the density of the said apex areabeing considerably greater and the thickness of said apex area beingconsiderably less than the density and thickness of the said lower halfof said cone body, the entire cone body and n extension consisting ofsubstantially the same brous material.

CLIFFORD E. STEVENS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,744,032 Baldwin Jan. 21, 19301,819,300 Newoombe Aug. 18, 1931 1,872,081 Hawley Aug. 16, 19321,947,362 Schoenhut Feb. 13, 1934 1,984,019 Hawley Dec. 11, 19342,030,501 Cunningham Feb. 11, 1936 2,146,975 Nagelvoort Feb. 14, 19392,234,007 Olson Mar. 4, 1941 2,288,832 Pare Julyr?, 1942 v2,408,038Brennan Sept. 24, 1946 2,411,066 Stevens Nov. 12, 1946 2,439,665 MarquisApr. 13, 1948

